Zero-delay Lightweight Defenses against Website Fingerprinting

Website Fingerprinting (WF) attacks threaten user privacy on anonymity networks because they can be used by network surveillants to identify the webpage being visited by extracting features from network traffic. A number of defenses have been put forward to mitigate the threat of WF, but they are flawed: some have been defeated by stronger WF attacks, some are too expensive in overhead, while others are impractical to deploy. In this work, we propose two novel zero-delay lightweight defenses, FRONT and GLUE. We find that WF attacks rely on the feature-rich trace front, so FRONT focuses on obfuscating the trace front with dummy packets. It also randomizes the number and distribution of dummy packets for traceto-trace randomness to impede the attacker's learning process. GLUE adds dummy packets between separate traces so that they appear to the attacker as a long consecutive trace, rendering the attacker unable to find their start or end points, let alone classify them. Our experiments show that with 33% data overhead, FRONT outperforms the best known lightweight defense, WTF-PAD, which has a similar data overhead. With around 22%-44% data overhead, GLUE can lower the accuracy and precision of the best WF attacks to a degree comparable with the best heavyweight defenses. Both defenses have no latency overhead. Table 1: Comparison of known WF defenses. For overhead, Low is a non-zero overhead up to 35%, Medium is roughly 35-70%, High is roughly 70-100%, and Very High is above 100%.